(The following may or may not constitute prior art)
Previous work on multiple mode optical fibers for mode-division multiplexing focused on step and graded index (GRIN) fiber designs for optimized two LP mode fibers (having three spatial modes). We have also disclosed GRIN fiber designs with 1% core relative deltas, including a shelf and trench in the cladding, which are optimized to support four LP modes (having six spatial modes).